This invention relates to a two cycle engine provided with a scavenging pump and more particularly to an improved scavenging system for a two cycle engine.
In order to improve the scavenging and performance of a two cycle engine, it has been proposed to provide a plurality of scavenge ports for each cylinder. These scavenge ports and the scavenge passages which serve them are oriented in such a way so as to achieve the desired scavenging pattern in the engine. Conventionally, it has been the practice to provide a scavenge manifold around the cylinder and from which the scavenge passages extend to serve their respective scavenge ports. A disadvantage with the prior art type of constructions is that the scavenge manifold, being cast or formed integrally within the cylinder block, has a relatively small effective cross-sectional area. Because of this, the air flow to the individual scavenge passages may not be as desired. That is, those scavenge passages which are closest to the air inlet will receive full air flow while those positioned more remotely will have their flow deteriorated due to the restriction of the scavenge manifold.
It is, therefore, a principal object of this invention to provide an improved scavenging arrangement for a two cycle internal combustion engine.
It is a further object of this invention to provide a scavenging system for a two cycle internal combustion engine wherein adequate air flow to all scavenge passages can be accomplished.
It is a further object of this invention to provide a plenum chamber within the cylinder block from which the scavenge passages are all served so as to ensure that the air flow to the individual scavenge passages will not be deteriorated by the flow to other scavenge passages.